Elevation of gamma-aminobutyric acid (GABA) and essential amino acids in vacuum impregnation mediated germinated rice traced by MALDI imaging

Rice is known to contain limiting amino acids. Synthesis of GABA in plants is an adaptive response by initiating glutamic acid. A higher rate of GABA production was observed in samples enriched with glutamic acid and vacuum impregnation (VI) with longer germination time. Heat map profiles classified GABA and essential amino acids into 1) small increments consisting of Arg, His and Met, 2) moderate increments consisting of GABA, Trp, Lys, Phe and Thr, and 3) large increments consisting of Ile, Leu and Val. In Jasmine rice, highest essential amino acids were found in samples soaked with water, enriched with glutamic acid, and germinated for 72–96 h. Highest GABA (44.8 mg/100 g) was noticed after VI for 20–40 min and germinated for 72–96 h. In Riceberry, highest GABA (74.2 mg/100 g) and essential amino acids were associated with samples treated with VI for 20–40 min and germinated for 96 h.